U.S. patent number 5,165,863 [Application Number 07/791,254] was granted by the patent office on 1992-11-24 for slant plate type compressor with variable capacity control mechanism.
This patent grant is currently assigned to Sanden Corporation. Invention is credited to Yukihiko Taguchi.
United States Patent |
5,165,863 |
Taguchi |
November 24, 1992 |
Slant plate type compressor with variable capacity control
mechanism
Abstract
A slant plate type compressor having a capacity or displacement
adjusting mechanism includes a housing for a cylinder block
provided with a plurality of cylinders and a crank chamber. A
piston is slidably fitted within each of the cylinders and is
reciprocated by a drive mechanism which includes a slant plate
having a surface with an adjustable incline angle. The incline
angle of the slant plate, and thus the capacity of the compressor,
is controlled according to the pressure differential between the
crank chamber and the suction chamber. The pressure in either the
crank chamber or the suction chamber is controlled by an externally
controlled valve mechanism which is disposed in a passageway
linking the crank chamber and the suction chamber. An internally
controlled safety valve device prevents an abnormal pressure
differential between the crank and suction chambers. The internally
controlled safety valve device is provided within the externally
controlled valve mechanism, thereby obtaining an easily
manufactured slant plate type compressor having a capacity
adjusting mechanism with a safety valve device.
Inventors: |
Taguchi; Yukihiko (Isesaki,
JP) |
Assignee: |
Sanden Corporation (Gunma,
JP)
|
Family
ID: |
26565701 |
Appl.
No.: |
07/791,254 |
Filed: |
November 13, 1991 |
Foreign Application Priority Data
|
|
|
|
|
Nov 16, 1990 [JP] |
|
|
2-308815 |
|
Current U.S.
Class: |
417/222.2;
417/270 |
Current CPC
Class: |
F04B
27/1804 (20130101); F04B 2027/1813 (20130101); F04B
2027/1831 (20130101); F04B 2027/1854 (20130101); F04B
2027/1859 (20130101); F04B 2027/189 (20130101) |
Current International
Class: |
F04B
27/18 (20060101); F04B 27/14 (20060101); F04B
001/28 () |
Field of
Search: |
;417/222R,222S,270 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
60-162087 |
|
Aug 1985 |
|
JP |
|
61-55380 |
|
Mar 1986 |
|
JP |
|
2153922A |
|
Aug 1985 |
|
GB |
|
Primary Examiner: Smith; Leonard E.
Attorney, Agent or Firm: Baker & Botts
Claims
I claim:
1. In a slant plate type refrigerant compressor having a compressor
housing enclosing a crank chamber, a suction chamber and a
discharge chamber therein, said compressor housing comprising a
cylinder block having a plurality of cylinders formed therethrough,
a piston slidably fitted within each of said cylinders, drive means
coupled to said pistons for reciprocating said pistons within said
cylinders, said drive means including a drive shaft rotatably
supported in said housing and coupling means for drivingly coupling
said drive shaft to said pistons such that rotary motion of said
drive shaft is converted into reciprocating motion of said pistons,
said coupling means including a slant plate having a surface
disposed at an adjustable inclined angle relative to a plane
perpendicular to said drive shaft, the inclined angle of said slant
plate being adjustable to vary the stroke length of said pistons in
said cylinders and to thereby vary the capacity of said compressor,
a passageway formed in said housing and linking said crank chamber
and said suction chamber in fluid communication, capacity control
means for varying the capacity of the compressor by adjusting the
inclined angle, and safety valve means for preventing an abnormal
pressure differential between said crank chamber and said suction
chamber, said capacity control means including externally
controlled valve means for controlling the opening and closing of
said passageway in response to changes in a plurality of external
signals to control the link between said crank and said suction
chambers and to thereby control the capacity of the compressor,
said externally controlled valve means being disposed in said
passageway, the improvement comprising:
said safety valve means being provided within said externally
controlled valve means so as to open said passageway when the
pressure differential between said crank chamber and said suction
chamber exceeds a predetermined value.
2. The compressor of claim 1 wherein said safety valve means opens
and closes said passageway in response to changes in the pressure
differential between said crank chamber and said suction
chamber.
3. The compressor of claim 1 wherein said externally controlled
valve means includes a valve element which opens and closes said
passageway and said safety valve means is disposed within said
valve element.
4. The compressor of claim 1 wherein said plurality of external
signals comprises a first signal representing a heat load on an
evaporator which is an element of a cooling circuit including said
compressor and a second signal representing an amount of demand for
acceleration of an automobile.
5. A slant plate type refrigerant compressor comprising:
a compressor housing enclosing a crank chamber, a suction chamber
and a discharge chamber;
said compressor housing including a cylinder block having a
plurality of cylinders formed therethrough, a piston slidably
fitted within each of said cylinders, and drive means coupled to
said pistons for reciprocating said pistons within said
cylinders;
said drive means including a drive shaft rotatably supported in
said housing and coupling means for drivingly coupling said drive
shaft to said pistons such that rotary motion of said drive shaft
is converted into reciprocating motion of said pistons;
said coupling means including a slant plate having a surface
disposed at an adjustable inclined angle relative to a plane
perpendicular to said drive shaft;
a passageway formed in said housing and linking said crank chamber
and said suction chamber in fluid communication;
capacity control means for varying the capacity of said compressor
by adjusting the inclined angle of said slant plate;
said capacity control means including externally controlled valve
means for controlling the opening and closing of said passageway;
and
safety valve means for preventing an abnormal pressure differential
between said crank chamber and said suction chamber;
wherein said externally controlled valve means is disposed in said
passageway;
wherein said safety valve means is disposed within said externally
controlled valve means so as to open said passageway when the
pressure differential between said crank chamber and said suction
chamber exceeds a predetermined value;
wherein the inclined angle of said slant plate is adjusted to vary
the stroke length of said pistons in said cylinders and to thereby
vary the capacity of said compressor; and
wherein said passageway is opened and closed in response to changes
in a plurality of external signals which control the link between
said crank chamber and said suction chamber, thereby controlling
the adjustment of the inclined angle of said slant plate and the
capacity of said compressor.
6. The compressor of claim 5 wherein said safety valve means opens
and closes said passageway in response to changes in the pressure
differential between said crank chamber and said suction
chamber.
7. The compressor of claim 5 wherein said externally controlled
valve means includes a valve element which opens and closes said
passageway and said safety valve means is disposed within said
valve element.
8. The compressor of claim 5 wherein said plurality of external
signals comprises a first signal representing a heat load on an
evaporator which is an element of a cooling circuit including said
compressor and a second signal representing an amount of demand for
acceleration of an automobile.
9. A variable displacement slant plate type compressor:
a compressor housing enclosing a crank chamber, a suction chamber
and a discharge chamber;
said compressor housing including a cylinder block having a
plurality of cylinders formed therethrough, a piston slidably
fitted within each of said cylinders, and drive means coupled to
said pistons for reciprocating said pistons within said
cylinders;
said drive means including a drive shaft rotatably supported in
said housing and coupling means for drivingly coupling said drive
shaft to said pistons such that rotary motion of said drive shaft
is converted into reciprocating motion of said pistons;
said coupling means including a slant plate having a surface
disposed at an adjustable inclined angle relative to a plane
perpendicular to said drive shaft;
a front end plate disposed on one end of said cylinder block and a
rear end plate disposed on the other end of said cylinder
block;
a cylindrical cavity having a first cavity portion and a second
cavity portion formed in said rear end plate, one end of said
cylindrical cavity communicating with the external environment;
a first passageway formed in said housing and linking in fluid
communication one of said crank chamber and said suction chamber
with said first cavity portion of said cylindrical cavity;
a second passageway formed in said housing and linking in fluid
communication the other of said crank chamber and said suction
chamber with said second cavity portion of said cylindrical
cavity;
capacity control means disposed in said cylindrical cavity;
said capacity control means including externally controlled valve
means for controlling fluid communication between said first cavity
portion and second cavity portion, and thus between said suction
chamber and said crank chamber, responsive to changes in a
plurality of external signals such that the capacity of the
compressor is thereby varied by adjusting the inclined angle of
said slant plate; and
safety valve means disposed within said externally controlled valve
means so as to open communication between said first cavity portion
and said second cavity portion when the pressure differential
between said crank chamber and said suction chamber exceeds
predetermined value, such that an abnormal pressure differential
between said crank chamber and said suction chamber is thereby
prevented.
10. The compressor of claim 9 wherein said plurality of external
signals includes a first signal representing a heat load on an
evaporator which is an element of a cooling circuit including said
compressor and a second signal representing the amount of demand
for acceleration of an automobile in which said compressor is
disposed.
11. The compressor of claim 9 wherein said capacity control
mechanism includes a first annular cylindrical casing made of
magnetic material and a second annular cylindrical casing having a
lower portion and an upper portion.
12. The compressor of claim 11 wherein an annular protrusion of
said second annular cylindrical casing forms a sealed boundary
between said first cavity portion and said second cavity portion of
said cylindrical cavity.
13. The compressor of claim 12 wherein an electromagnetic coil is
disposed within said first annular cylindrical casing.
14. The compressor of claim 13 wherein said externally controlled
valve means includes a valve member disposed within said second
annular cylindrical casing, said valve member having a first larger
diameter axial hole and a second smaller diameter axial hole
extending therefrom and communicating with the interior of said
second annular cylindrical casing.
15. The compressor of claim 14 wherein said valve member further
includes a first radial hole such that one of said first axial hole
and said second axial hole is in fluid communication with an
interior region of said lower portion of said second annular
cylindrical casing.
16. The compressor of claim 15 wherein said lower portion of said
second annular cylindrical casing includes a plurality of radial
holes so as to link the interior region of said lower portion of
said second annular cylindrical casing with said first cavity
portion of said cylindrical cavity.
17. The compressor of claim 16 wherein said upper portion of said
second annular casing cylindrical casing includes a plurality of
radial holes so as to link in fluid communication the interior
region thereof and said second cavity portion of said cylindrical
cavity.
18. The compressor of claim 17 wherein said safety valve means
includes a ball member elastically supported by a coil spring and
disposed within said first axial hole of said valve member such
that fluid communication between said first axial hole and said
second axial hole is blocked.
19. The compressor of claim 18 wherein an upper surface of said
ball member is in communication with and urged downwardly by the
pressure in one of said suction chamber and said crank chamber
while a lower surface of said ball member is in communication with
and urged upwardly by the pressure in the other of said suction
chamber and said crank chamber.
20. The compressor of claim 18 wherein said ball member opens said
second axial hole thereby allowing fluid communication with said
first axial hole when the pressure differential between said crank
chamber and said suction chamber reaches a predetermined value.
21. The compressor of claim 17 wherein said valve member is moved
so as to maintain a predetermined constant pressure in said suction
chamber.
22. The compressor of claim 17 wherein said valve member is moved
so as to maintain a predetermined constant pressure in said crank
chamber.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a refrigerant compressor, and more
particularly, to a slant plate type compressor, such as a wobble
plate type compressor, having a variable displacement mechanism
which is suitable for use in an automobile air conditioning
system.
2. Description of the Prior Art
Slant plate type piston compressors including variable displacement
or capacity adjusting mechanisms for controlling the compression
ratio of a compressor in response to demand are generally known in
the art. For example, Japanese Utility Model Application
Publication No. 63-134181 discloses a wobble plate type compressor
including a cam rotor driving device and a wobble plate linked to a
plurality of pistons. Rotation of the cam rotor driving device
causes the wobble plate to nutate and thereby successively
reciprocate the pistons in the corresponding cylinders. The stroke
length of the pistons and thus the capacity of the compressor may
be easily changed by adjusting the slant angle of the wobble plate.
The slant angle is changed in response to the pressure differential
between the suction chamber and the crank chamber.
In the above-mentioned Japanese Utility Model Application
Publication, the crank chamber and the suction chamber are linked
in fluid communication by a first path or passageway. A valve
mechanism is disposed in the first passageway in order to control
fluid communication between the crank and suction chambers by the
opening and closing of the first passageway. The valve mechanism
generally includes a solenoid, a plunger and a valve member
disposed on one end of the plugner. The solenoid receives two
external signals, one of which represents the heat load on an
evaporator of a cooling circuit and another which represents the
amount of demand for accelerating an automobile.
The solenoid induces various electromagnetic forces in response to
changes in the two external signals and thereby changes the axial
position of the plunger so that the first passageway is opened and
closed by the valve member. Hence, the angular position of the
wobble plate is varied in a range from the maximum to the minimum
slant angles responsive to changes in the two external signals such
that the capacity displacement of the compressor is thereby
adjusted and the suction chamber pressure is maintained at a
predetermined constant value.
The compressor further includes a second passageway, separate from
the first passageway, and communicating the crank chamber with the
suction chamber. A safety valve device including a ball member and
a coil spring elastically supporting the ball member is disposed in
the second passageway. The safety valve device opens and closes the
second passageway in response to changes in the pressure
differential between the crank chamber and the suction chamber. The
second passageway is opened when the pressure differential between
the crank chamber and the suction chamber exceeds a predetermined
value. Therefore, when communication between the crank chamber and
the suction chamber is blocked for a long time period of time due
to trouble in the valve mechanism, thereby causing an abnormal rise
in the crank chamber pressure because of blow-by gas leaking past
the pistons in the cylinders as the pistons reciprocate, the second
passageway is opened so as to forcibly and quickly reduce the crank
chamber pressure and thereby prevent an abnormal pressure
differential between the crank and suction chambers. As a result,
excessive friction between the internal component parts of the
compressor caused by the abnormal differential between the crank
chamber and the suction chamber can be prevented.
In this prior art embodiment, however, the second passageway is
separate from the first passageway such that the process of forming
the second passageway and the process of disposing the safety valve
device in the second passageway are additional steps required
during the manufacturing of the compressor. Accordingly, the
manufacturing process of the compressor is complicated by this
requirement.
Therefore, a strong need exists for a compressor having a variable
displacement control mechanism which can be easily manufactured and
which can prevent an abnormal pressure differential between the
crank chamber and the suction chamber.
SUMMARY OF THE INVENTION
A slant plate type refrigerant compressor including a compressor
housing enclosing a crank chamber, a suction chamber and a
discharge chamber therein is disclosed. The compressor housing
includes a cylinder block having a plurality of cylinders formed
therethrough, and a piston slidably fitted within each of the
cylinders. A drive mechanism is coupled to the pistons for
reciprocating the pistons within the cylinders. The drive mechanism
includes a drive shaft rotatably supported in the housing and a
coupling mechanism which drivingly couples the drive shaft to the
pistons such that the rotating motion of the drive shaft is
converted into reciprocating motion of the pistons. The coupling
mechanism includes a slant plate having a surface disposed at an
adjustable inclined angle relative to a plane perpendicular to the
drive shaft. The inclined angle of the slant plate is adjustable to
vary the stroke length of the pistons in the cylinders and to
thereby vary the capacity of the compressor. A passageway is formed
in the housing and links the crank chamber and the suction chamber
in fluid communication.
The compressor further includes a safety valve device for
preventing an abnormal pressure differential between the crank
chamber and the suction chamber, and a capacity control device for
varying the capacity of the compressor by adjusting the inclined
angle. The capacity control device includes an externally
controlled valve mechanism which is disposed in the passageway. The
externally controlled valve mechanism controls the opening and
closing of the passageway in response to changes in a plurality of
external signals which thereby control the capacity of the
compressor. The safety valve device is provided within the
externally controlled valve mechanism in order to open the
passageway when a pressure differential between the crank chamber
and the suction chamber exceeds a predetermined value.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical longitudinal sectional view of a slant plate
type refrigerant compressor including a capacity control mechanism
according to a first embodiment of this invention.
FIG. 2 is an enlarged partial sectional view of the capacity
control mechanism shown in FIG. 1.
FIG. 3 is a graph showing the relationship between the amperage of
an electric current supplied from an electric circuit to an
electromagnetic coil and the corresponding suction chamber pressure
at which the upward and downward forces acting on a diaphragm are
balanced.
FIG. 4 is a graph showing the changes in pressure differential
between the crank and suction chambers over a period of time after
the supply of electric current having a predetermined maximum
amperage from an electric circuit to an electromagnetic coil is
initiated.
FIG. 5 is a vertical longitudinal sectional view of a slant plate
type refrigerant compressor including a capacity control mechanism
according to a second embodiment of this invention.
FIG. 6 is an enlarged partial sectional view of the capacity
control mechanism shown in FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIGS. 1 and 5, for purpose of explanation only, the left side of
the figures will be referenced as the forward end or front of the
compressor, and the right side of the figures will be referenced as
the rearward end or rear of the compressor.
With reference to FIG. 1, the construction of a slant plate type
compressor, and more specifically a wobble plate type refrigerant
compressor 10, having a capacity control mechanism in accordance
with a first embodiment of the present invention is shown.
Compressor 10 includes cylindrical housing assembly 20 including
cylinder block 21, front end plate 23 disposed at one end of
cylinder block 21, crank chamber 22 enclosed within cylinder block
21 by front end plate 23, and rear end plate 24 attached to the
other end of cylinder block 21. Front end plate 23 is mounted on
cylinder block 21 forward of crank chamber 22 by a plurality of
bolts 101. Rear end plate 24 is also mounted on cylinder block 21
at the opposite end by a plurality of bolts (not shown). Valve
plate 25 is located between rear end plate 24 and cylinder block
21. Opening 231 is centrally formed in front end plate 23 for
supporting drive shaft 26 by bearing 30 disposed therein. The inner
end portion of drive shaft 26 is rotatably supported by bearing 31
disposed within central bore 210 of cylinder block 21. Bore 210
extends to a rear end surface of cylinder block 21.
Bore 210 includes thread portion 211 formed at an inner peripheral
surface of a central region thereof. Adjusting screw 220 having a
hexagonal central hole 221 is screwed into thread portion 211 of
bore 210. Circular disc-shaped spacer 230 having central hole 259
is disposed between the inner end surface of drive shaft 26 and
adjusting screw 220. Axial movement of adjusting screw 220 is
transferred to drive shaft 26 through spacer 230 so that all three
elements move axially within bore 210. The above-mentioned
construction and functional manner are described in detail in U.S.
Pat. No. 4,948,343 to Shimizu.
Cam rotor 40 is fixed on drive shaft 26 by pin member 261 and
rotates with drive shaft 26. Thrust needle bearing 32 is disposed
between the inner end surface of front end plate 23 and the
adjacent axial end surface of cam rotor 40. Cam rotor 40 includes
arm 41 having pin member 42 extending therefrom. Slant plate 50 is
disposed adjacent cam rotor 40 and includes opening 53. Drive shaft
26 is disposed through opening 53. Slant plate 50 includes arm 51
having slot 52. Cam rotor 40 and slant plate 50 are connected by
pin member 42, which is inserted in slot 52 to create a hinged
joint. Pin member 42 is slidable within slot 52 to allow adjustment
of the angular position of slant plate 50 with respect to a plane
perpendicular to the longitudinal axis of drive shaft 26. A balance
weight ring 80 having a substantial mass is disposed on a nose of
hub 54 of slant plate 50 in order to balance the slant plate 50
under dynamic operating conditions. Balance weight ring 80 is held
in place by means of retaining ring 81.
Wobble plate 60 is nutatably mounted on hub 54 of slant plate 50
through bearings 61 and 62 which allow slant plate 50 to rotate
with respect to wobble plate 60. Fork-shaped slider 63 is attached
to the radially outer peripheral end of wobble plate 60 and is
slidably mounted about sliding rail 64 disposed between front end
plate 23 and cylinder block 21. Fork-shaped slider 63 prevents the
rotation of wobble plate 60 such that wobble plate 60 nutates along
rail 64 when cam rotor 40, slant plate 50 and balance weight ring
80 rotate. Undesirable axial movement of wobble plate 60 on hub 54
of slant plate 50 is prevented by contact between a rear end
surface of inner annular projection 65 of wobble plate 60 and a
front end surface of balance weight ring 80. Cylinder block 21
includes a plurality of peripherally located cylinder chambers 70
in which pistons 71 are disposed. Each piston 71 is connected to
wobble plate 60 by a corresponding connecting rod 72. Accordingly,
nutation of wobble plate 60 thereby causes pistons 71 to
reciprocate within their respective chambers 70.
Rear end plate 24 includes peripherally located annular suction
chamber 241 and centrally located discharge chamber 251. Valve
plate 25 includes a plurality of valved suction ports 242 linking
suction chamber 241 with respective cylinders 70. Valve plate 25
also includes a plurality of valved discharge ports 252 linking
discharge chamber 251 with respective cylinders 70. Suction ports
242 and discharge ports 252 are provided with suitable reed valves
as described in U.S. Pat. No. 4,011,029 to Shimizu.
Suction chamber 241 includes inlet portion 241a which is connected
to an evaporator (not shown) of the external cooling circuit.
Discharge chamber 251 is provided with outlet portion 251a
connected to a condenser (not shown) of the cooling circuit.
Gaskets 27 and 28 are located between cylinder block 21 and the
inner surface of valve plate 25 and between the outer surface of
valve plate 25 and rear end plate 24, respectively, to seal the
mating surfaces of cylinder block 21, valve plate 25 and rear end
plate 24. Gaskets 27 and 28 and valve plate 25 thus form valve
plate assembly 200. A steel valve retainer 253 is fixed on a
central region of the outer surface of valve plate 25 by bolt 254
and nut 255. Valve retainer 253 prevents excessive bend of the reed
valve which is provided at discharge port 252 during a compression
stroke of piston 71.
Conduit 18 is axially bored through cylinder block 21 so as to link
crank chamber 22 to discharge chamber 251 through hole 181 which is
axially bored through valve plate assembly 200. A throttling device
such as orifice tube 182, is fixedly disposed within conduit 18.
Filter member 183 is disposed in conduit 18 at the rear of orifice
tube 182. Accordingly, a portion of the discharged refrigerant gas
in discharge chamber 251 always flows into crank chamber 22 with a
reduced pressure generated by orifice tube 182. The above-mentioned
construction and functional manner are described in detail in
Japanese Patent Application Publication No. 1-142277.
Rear end plate 24 further includes bulged portion 243 radially
extending from a central region to a radial end thereof.
Cylindrical cavity 244 is formed in bulged portion 243 so as to
accommodate capacity control mechanism 400 which is further
discussed below. One end of cavity 244 is open to the external
environment outside of the compressor, that is, to atmospheric
conditions.
With reference to FIG. 2 additionally, cylindrical cavity 244
includes large, intermediate, and small diameter portions 244a,
244b and 244c, respectively, which thereby from an axial outer end
thereof. The diameter of intermediate diameter portion 244b is
smaller than the diameter of large diameter portion 244a, and is
greater than the diameter of small diameter portion 244c. Large
diameter portion 244a is linked to intermediate diameter portion
244b through truncated cone portion 244d. Large diameter portion
244a of cavity 244 is linked to suction chamber 241 through conduit
245 which is formed in rear end plate 24. Conduit 246 is also
formed in rear end plate 24 so as to link small diameter portion
244c of cavity 244 to hole 256 which is formed in valve plate
assembly 200. Hole 256 is linked to central bore 210 through
conduit 212 which is formed in the rear portion of cylinder block
21. Central bore 210 is linked to crank chamber 22 through gap 31a
created between bearing 31 and the inner peripheral surface of
central bore 210, hole 231 of spacer 230 and hole 221 of adjusting
screw 220. Accordingly, small diameter portion 244c of cavity 244
is linked to crank chamber 22 via conduit 246, hole 256, conduit
212, central bore 210, hole 221, hole 231 and gap 31a.
Capacity control mechanism 400 includes a first annular cylindrical
casing 410 of magnetic material accommodated in large diameter
portion 244a of cavity 244 and a second annular cylindrical casing
420 having a large diameter section 421 and a small diameter
section 422 which extends upwardly from a top end of large diameter
section 421. Large diameter section 421 of second annular
cylindrical casing 420 is fixedly disposed at a top end of first
annular cylindrical casing 410. The top end of small diameter
section 422 of second annular cylindrical casing 420 terminates at
a point approximately half the lenght of small diameter portion
244c of cavity 244. Annular protrusion 423 is formed at a boundary
between large and small diameter sections 421 and 422 of second
annular cylindrical casing 420, and is disposed within intermediate
diameter portion 244b of cavity 244. An O-ring seal element 423a is
disposed in an annular groove 423b formed at the outer peripheral
surface of annular protrusion 423 so as to seal the mating surfaces
between the outer peripheral surface of annular protrusion 423 and
the inner peripheral surface of intermediate diameter portion 244b
of cavity 244. Thus, small diameter portion 244c of cavity 244 is
sealingly insulated from large diameter portion 244a of cavity
244.
First annular cylindrical casing 410 includes an annular flange
411, which radially and inwardly extends from the top portion of
first annular cylindrical casing 410, and an axial annular
projection 412 which axially and downwardly extends from an inner
peripheral end portion of annular flange 411. Axial annular
projection 412 terminates at a point approximately one-third of the
length of first annular cylindrical casing 410, and includes a
tapered bottom end surface 412a. Cylindrical pipe member 413, the
length of which is a little less than the length of first annular
cylindrical casing 410, is disposed in first annular cylindrical
casing 410. An upper end portion of cylindrical pipe member 413 is
fixedly attached to the outer peripheral surface of axial annular
projection 412 by forcible insertion. Annular disc plate 414 is
fixedly disposed at a bottom end of first annular cylindrical
casing 410 to define an annular cavity 415 formed in cooperation
with cylindrical pipe member 413 and first annular cylindrical
casing 410. Electromagnetic coil 430 is fixedly disposed within
annular cavity 415. Annular cylindrical pedestal 440 is disposed at
the bottom portion of cylindrical pipe member 413. The upper half
portion of pedestal 440 is fixedly attached to an inner peripheral
surface of the bottom portion of cylindrical pipe member 413 by
forcible insertion.
A vacant space 450 is defined by cylindrical pipe member 413,
annular cylindrical pedestal 440 and axial annular projection 412
of first annular cylindrical casing 410. Cylindrical member 451 of
magnetic material is axially and movably disposed in vacant space
450. Cylindrical rod 460 having circular disc plate 461 at its top
end loosely penetrates through axial annular projection 412. The
bottom end portion of rod 460 is fixedly received in cylindrical
hole 451a formed in the top end surface of cylindrical member 451
through forcible insertion. Cylindrical member 451 includes tapered
top end surface 451b which is parallel to the tapered bottom end
surface 412a of axial annular projection 412. Annular cylindrical
pedestal 440 includes a thread portion 441 formed in the inner
peripheral surface of the lower half portion thereof. Adjusting
screw 442 is screwed into thread portion 441 formed in the inner
peripheral surface of the lower half of annular cylindrical
pedestal 440. First coil spring 470 is disposed between adjusting
screw 442 and the top end surface of cylindrical hole 451c which is
formed at the bottom end surface of cylindrical member 451. The
restoring force of first coil spring 470 urges cylindrical member
451 upwardly, thereby urging rod 460 upwardly. The restoring force
of first coil spring 470 is adjusted by changing in the axial
position of adjusting screw 442.
When electromagnetic coil 430 is energized, an electromagnetic
force which tends to move cylindrical member 451 upwardly is
induced. The magnitude of the electromagnetic force is directly
proportional to the amperage of an electric current that is
supplied to electromagnetic coil 430 from an electric circuit (not
shown). The electric circuit receives a signal representing the
heat load on the evaporator, such as the temperature of air
immediately before passing through the evaporator, and the signal
representing the amount of demand for acceleration of the
automobile, such as the magnitude of force stepping on the
accelerator. After processing the two signals, an electric current
is supplied from the electric circuit to electromagnetic coil 430
in response to changes in the values of the two signals. The
amperage of the electric current is continuously varied within the
range from zero ampere to a predetermined maximum amperage, for
example, 1.0 ampere.
More precisely, when the heat load on the evaporator is excessively
large, such that the temperature of air immediately before passing
through the evaporator is excessively high, and when the amount of
demand for acceleration of the automobile is small, an electric
current having zero ampere, i.e., no electric current, is supplied
from the electric circuit to the electromagnetic coil 430 after the
processing of the two signals through the electric circuit.
However, when the amount of demand for acceleration of the
automobile exceeds a predetermined value, the signal representing
the demand for acceleration overrides the signal representing the
heat load on the evaporator in the processing of the two signals by
the electric circuit. As a result, an electric current having the
predetermined maximum amperage is supplied from the electric
circuit to the electromagnetic coil 430 even though the heat load
on the evaporator is excessively large. Furthermore, when the heat
load on the evaporator is excessively small, such as when the
temperature of air immediately before passing through the
evaporator is excessively low, an electric current having the
predetermined maximum amperage is supplied from the electric
circuit to the electromagnetic coil 430 without regard to the
amount of demand for acceleration of the automobile.
O-ring seal element 416 is disposed in annular groove 417 formed in
the outer peripheral surface of the bottom end portion of first
annular cylindrical casing 410, to thereby seal the mating surfaces
between the outer peripheral surface of first annular cylindrical
casing 410 and the inner peripheral surface of large diameter
portion 244a of cavity 244. Thus, large diameter portion 244a of
cavity 244 is sealingly insulated from the ambient atmosphere
outside of the compressor. Snap ring 431 is fixedly disposed at the
bottom end of the inner peripheral surface of cavity 244 so as to
prevent capacity control mechanism 400 from falling out of cavity
244.
Valve member 480 is disposed in the inner space of large diameter
section 421 of second annular cylindrical casing 420. First axial
hole 481 is centrally formed in valve member 480 and is open
through to the bottom end of valve member 480. Valve member 480 is
provided with circular plate 482 fixedly disposed at the bottom end
thereof so as to close the bottom opening of first axial hole 481.
First axial hole 481 terminates after extending approximately
two-thirds of the length through valve member 480. The diameter of
the terminal end portion of first axial hole 481 gradually
decreases upwardly so as to form a valve seat 483. Second axial
hole 484 having a diameter smaller than the diameter of first axial
hole 481, is centrally formed in the top portion of valve member
480 so as to link first axial hole 481 to the interior space of
small diameter section 422 of second annular cylindrical casing
420. Ball member 485a is elastically supported by a second coil
spring 485b, the bottom end thereof being disposed at circular
plate 482 such that ball member 485a is urged upwardly by virtue of
the restoring force of second coil spring 485b. In a preferred
embodiment of the invention, ball member 485a and second coil
spring 485b substantially form safety valve device 485, as further
discussed below. Annular ring member 486, through which valve
member 480 slidably moves in the axial direction is fixedly
disposed at the inner peripheral surface of large diameter section
421 of second annular cylindrical casing 420 by forcible insertion.
Valve member 480 includes a truncated cone portion 487 formed at
the top end thereof. Radial hole 488 is formed in a side wall of
valve member 480 so as to link the inner space of large diameter
section 421 of second annular cylindrical casing 420 to first axial
hole 481 of valve member 480. A plurality of radial holes 424 are
formed in large diameter section 421 of second annular cylindrical
casing 420 so as to link large diameter portion 244a of cavity 244
to the interior region of large diameter sectin 421 of second
annular cylindrical casing 420.
First annular ridge 489 is formed in the inner peripheral surface
of annular casing 420 at the boundary between large and small
diameter sections 421 and 422 of annular casing 420. First annular
ridge 489 functions as a valve seat which truncated cone portion
487 of valve member 480 contacts. Second annular ridge 490 is
formed in a top portion of the inner peripheral surface of small
diameter section 422 of annular casing 420 by reducing the inner
diameter thereof. Third coil spring 491 is disposed within the
inner space of small diameter section 422. The top end of third
coil spring 491 contacts second annular ridge 490 and the bottom
end of third coil spring 491 contacts the flat top surface of valve
member 480. Therefore, valve member 480 is urged downwardly by the
restoring force of third coil spring 491. A plurality of radial
holes 492 are formed in small diameter section 422 of second
annular cylindrical casing 420 so as to link small diameter portion
244c of cavity 224 to the interior region of small diameter section
422 of second annular cylindrical casing 420.
Diaphragm 418 is disposed between disc plate 461 of rod 460 and
circular plate 482 of valve member 480. The top surface of the
central region of diaphragm 418 is maintained in contact with the
bottom surface of circular plate 482 of valve member 480 by virtue
of the restoring force of third coil spring 491. Similarly, the
bottom surface of the central region of diaphragm 418 is maintained
in contact with the top surface of disc plate 461 of rod 460 by
virtue of the restoring of first coil spring 470.
An outer peripheral portion of diaphragm 418 is sandwiched between
annular flange 411 of first annular cylindrical casing 410 and
flange 425 which radially and outwardly extends from the bottom end
of second annular cylindrical casing 420. O-ring seal element 419
is disposed between the top end surface of flange 411 of casing 410
and the bottom end surface of the outer peripheral portion of
diaphragm 418 to thereby effectively seal the mating surfaces
therebetween.
Indent 411a is formed at the top end surface of the inner
peripheral portion of annular flange 411 of casing 410 such that
indent 411a faces the bottom end surface of diaphragm 418. Indent
411a is linked to the ambient atmosphere outside of the compressor
via the gap 412b created between rod 460 and annular projection
412, vacant space 450, the gap 440a created between pedestal 440
and pipe member 413, and the gap 440b created between pedestal 440
and adjusting screw 442. Thus, the bottom end surface of diaphragm
418 is in communication with and thereby receives air at
atmospheric pressure.
Similarly, the interior region of the large diameter section 421 of
second casing 420 is linked to suction chamber 241 via holes 424,
large diameter portion 244a of cavity 244, and conduit 245. Thus,
the top end surface of diaphragm 418 is in communication with and
thereby receives the refrigerant at the suction chamber
pressure.
During operation of compressor 10, drive shaft 26 is rotated by the
engine of the automobile through electromagnetic clutch 300. Cam
rotor 40 is rotated with drive shaft 26, thereby rotating slant
plate 50 as well, which in turn causes wobble plate 60 to nutate.
The nutational motion of wobble plate 60 then reciprocates pistons
71 in their respective cylinders 70. As pistons 71 are
reciprocated, refrigerant gas is introduced into suction chamber
241 through inlet portion 241a, flows into each cylinder 70 through
suction ports 242, and is then compressed. The compressed
refrigerant gas is then discharge to discharge chamber 251 from
each cylinder 70 through discharge ports 252, and continues
therefrom into the cooling circuit through outlet portion 251a.
The capacity of compressor 10 is adjusted in order to maintain a
constant pressure in suction chamber 241, irrespective of the
changes in the heat load on the evaporator or the rotating speed of
the compressor. The capacity of the compressor is adjusted by
changing the angle of the slant plate, which is dependent upon the
crank chamber pressure, or more precisely, which is dependent upon
the differential between the crank chamber and the suction chamber
pressures. During the operation of compressor 10, the pressure of
the crank chamber increases due to blow-by gas flowing past pistons
71 as they reciprocate in cylinders 70. As the crank chamber
pressure increases relative to the suction chamber pressure, the
slant angle of slant plate 50 as well as the slant angle of wobble
plate 60 decrease, thereby decreasing the capacity of the
compressor. Likewise, a decrease in the crank chamber pressure
relative to the suction chamber pressure causes an increase in the
angle of slant plate 50 and wobble plate 60, and thus an increase
in the capacity of the compressor.
The operation of capacity control mechanism 400 of compressor 10 in
accordance with the first embodiment of the present invention is
carried out in the following manner. With reference to FIGS. 1-3,
when the heat load on the evaporator is excessively large and
concurrently therewith the amount of demand for acceleration of the
automobile is small, no electric current is supplied from the
electric circuit to the electromagnetic coil 430. As a result,
diaphragm 418 is urged upwardly only by virtue of the restoring
force of first coil spring 470 and the atmospheric pressure force
acting on the bottom end surface of diaphragm 418. Under such
conditions, valve member 480 is situated so as to maintain an
opening for communication between small diameter portion 244c of
cavity 244 and large diameter portion 244a of cavity 244. Valve
member 480 maintains such a position until the suction chamber
pressure drops to a first predetermined value, for example 1.0
kg/cm.sup.2 G, at which time the upward and downward forces acting
on diaphragm 418 will be balanced. Thus, slant plate 50 and wobble
plate 60 are disposed at a maximum slant angle with respect to the
plane perpendicular to the longitudinal axis of drive shaft 26 due
to an opening for fluid communication between crank chamber 22 and
suction chamber 241; and accordingly, compressor 10 operates in a
maximum capacity displacement until the suction chamber pressure
drops to the first predetermined value. Once the suction chamber
pressure drops to the first predetermined value, the slant angle of
slant plate 50 and wobble plate 60 is adjusted in response to the
changes in the heat load on the evaporator in order to thereby
maintain the suction chamber pressure at the first predetermined
value.
On the other hand, when the heat load on the evaporator is
excessively small, an electric current having a predetermined
maximum amperage is supplied from the electric circuit to the
electromagnetic coil 430 without regard to the amount of demand for
acceleration of the automobile. As a result, diaphragm 418 is urged
upwardly by virtue of the restoring force of first coil spring 470,
a predetermined maximum electromagnetic force induced by
electromagnetic coil 430, and the atmospheric pressure force acting
on the bottom end surface of diaphragm 418. Valve member 480 thus
moves upwardly so as to close the fluid communication opening
between small diameter portion 244c of cavity 244 and large
diameter portion 244a of cavity 244. Valve member 480 maintains
such a position until the suction chamber pressure rises to a
second predetermined value, for example 4.0 kg/cm.sup.2 G, at which
time the upward and downward forces acting on diaphragm 418 are
balanced. Therefore, slant plate 50 and wobble plate 60 are
disposed at a minimum slant angle with respect to the plane
perpendicular to the longitudinal axis of drive shaft 26 due to the
block in fluid communication between crank chamber 22 and suction
chamber 241; and accordingly, compressor 10 operates at a minimum
capacity displacement until the suction chamber pressure rises to
the second predetermined value. Once the suction chamber pressure
rises to the second predetermined value, the slant angle of slant
plate 50 and wobble plate 60 is adjusted in response to the changes
in the heat load on the evaporator in order to thereby maintain the
suction chamber pressure at the second predetermined value.
Furthermore, since the amperage of the electric current supplied
from the electric circuit to electromagnetic coil 430 is
continuously varied within the range from zero to the predetermined
maximum value in response to the changes in the value of the
aforementioned two signals, the location of valve member 480 is
likewise continuously varied in response to these amperage changes.
Therefore, as shown in FIG. 3, the suction chamber pressure at
which the upward and downward forces acting on diaphragm 418 are
balanced is also continuously varied within the range defined by
the first and second predetermined values. Thus, the angular
position of slant plate 50 and wobble plate 60 is continuously
varied within a range defined by the maximum and minimum slant
angles and the capacity displacement of compressor 10 is similarly
varied within a range defined by the maximum and the minimum values
thereof.
According to the above-mentioned manner of operation for capacity
control mechanism 400, the capacity displacement of compressor 10
is adjusted to maintain a predetermined constant pressure in
suction chamber 241.
Furthermore, when the demand for acceleration of the automobile
exceeds the predetermined value at a time when the suction chamber
pressure is being maintained at the first predetermined value,
i.e., 1.0 kg/cm.sup.2 G, the angular position of slant plate 50 and
wobble plate 60 is forcibly changed to, and then is maintained at
the minimum slant angle until the suction chamber pressure rises to
the second predetermined value, i.e., 4.0 kg/cm.sup.2 G. This
maximally reduces the energy consumption by the compressor, the
driving force which is derived from the automobile engine, and
thereby assists in providing the acceleration that is demanded.
In other words, in a situation where electromagnetic coil 430 is
receiving an electric current having zero ampere or approximate
zero ampere from the electric circuit is suddenly changed such that
electromagnetic coil 430 is receiving an electric current having
the predetermined maximum amperage, i.e., 1.0 ampere from the
electric circuit, the location of valve member 480 is forcibly
moved and then maintained so as to close the fluid communication
opening between small diameter portion 244c of cavity 244 and large
diameter portion 244a of cavity 244, until such a time that the
suction chamber pressure rises to the second predetermined value,
i.e., 4.0 kg/cm.sup.2 G.
As a result, the block in fluid communication between crank chamber
22 and suction chamber 241 is maintained for a long time period. If
a safety valve device, such as discussed in the description of the
prior art, is not provided in the compressor, this long time period
of a block in the fluid communication between crank chamber 22 and
suction chamber 241 causes an abnormal rise in the crank chamber
pressure due to the conduction of the refrigerant gas from
discharge chamber 251 to crank chamber 22 through conduit 18 having
orifice tube 182, and blow-by gas leaking past pistons 71 in
cylinder chambers 70 as the pistons 71 reciprocate. Thus, the
pressure differential between the crank chamber 22 and the suction
chamber 241 becomes excessively large, as shown by the dashed line
in FIG. 4, and a force excessively urging wobble plate 60
rearwardly is generated. This excessive urging force on wobble
plate 60 causes excessive rearward movement of wobble plate 60, and
thereby results in excessive friction between the rear end surface
of annular projection 65 of wobble plate 60 and the front end
surface of balance weight ring 80, and between the inner end
surface of drive shaft 26 and a front end surface of spacer 230
disposed in central bore 210. This excessive friction may in turn
then cause a seizure between annular projection 65 of wobble plate
60 and balance weight ring 80 or between drive shaft 26 and spacer
230.
In order to resolve the above defect, capacity control mechanism
400 is provided with safety valve device 485 therein. Safety valve
device 485 includes ball member 485a and second coil spring 485b
which elastically supports ball member 485a. Safety valve device
485 functions in the following manner. Ball member 485a is urged
downwardly by the crank chamber pressure received on the upper
spherical surface thereof while also being urged upwardly by the
restoring force of second coil spring 485b and the suction chamber
pressure received on the lower spherical surface thereof. Safety
valve device 485 is designed so as to open second axial hole 484
when the pressure differential between crank chamber 22 and suction
chamber 241 rises to a predetermined value, for example, 2.0
kg/cm.sup.2. Therefore, the crank chamber pressure is forcibly and
quickly reduced so as to maintain the pressure differential between
crank chamber 22 and suction chamber 241 at the predetermined
value, i.e., 2.0 kg/cm.sup.2, as shown by the solid line in FIG. 4,
and thereby maintain the angular position of slant plate 50 and
wobble plate 60 at the minimum slant angle even when the amperage
of the electric current is suddenly increased from zero ampere to
the predetermined maximum amperage. Thus, generation of an
excessive force which urges wobble plate 60 rearwardly can be
prevented and the resultant excessive friction between the rear end
surface of annular projection 65 of wobble plate 60 and the front
end surface of balance weight ring 80, and between the inner end
surface of drive shaft 26 and the front end surface of spacer 230
disposed in central bore 210 can also be prevented. Furthermore,
safety valve device 485 functions equally as well when the fluid
communication opening between crank chamber 22 and suction chamber
241 is blocked for a long time period due to problems with the
movement of valve member 480.
As discussed above, since capacity control mechanism 400 is
provided with safety valve device 485 therein, the complicated
process of forming an additional passageway for communicating crank
chamber 22 with suction chamber 241 in cylinder block 21 and the
process of disposing the safety valve device in the additional
passageway, are thus eliminated. Therefore, according to the
present invention, a compressor having an externally controlled
capacity control mechanism and a safety valve device for preventing
an abnormal pressure differential between the crank and suction
chambers can be easily manufactured.
With reference to FIG. 5, a wobble plate type refrigerant
compressor including a capacity control mechanism in accordance
with a second embodiment of the present invention is shown. As
illustrated, like reference numerals are used to denote like
elements corresponding to those shown in FIGS. 1 and 2. Except
where otherwise stated, the overall functioning of the compressor
is the same as discussed above.
With reference to FIG. 6 in addition to FIG. 5, capacity control
mechanism 500 of the wobble plate type refrigerant compressor
includes a valve member 580 disposed in the interior region of
large diameter section 421 of second annular cylindrical casing
420. First axial hole 581 is centrally formed in valve member 580,
and is open through to the top end of valve member 580. First axial
hole 581 terminates at a point corresponding to half of the length
of valve member 580. The diameter of the terminal end portion of
first axial hole 581 is gradually decreased downward so as to form
a valve seat 582. Second axial hole 583, having a diameter smaller
than the diameter of first axial hole 581, extends from the
terminal end of first axial hole 581 to the bottom end portion of
valve member 580. Ball member 584a is disposed in valve seat 582.
Annular ring member 585, through which valve member 580 slidably
moves along the longitudinal axis, is fixedly disposed at the inner
peripheral surface of large diameter section 421 of second annular
cylindrical casing 420 by forcible insertion. Valve member 580
includes a truncated cone portion 586 formed at the top end
thereof. The inner space of large diameter section 421 of second
annular cylindrical casing 420 is linked to second axial hole 583
of valve member 580 through radial hole 488.
Third coil spring 587 is elastically disposed between truncated
cone portion 586 of valve member 580 and an annular ridge 588 which
is formed at the inner peripheral surface of the boundary region
between large and small diameter sections 421 and 422 of second
annular cylindrical casing 420. Valve member 580 is urged
downwardly by virtue of the restoring force of third coil spring
587.
Second annular cylindrical casing 420 further includes a thread
portion 589 formed at the inner peripheral surface of the top end
portion thereof. Adjusting screw 590 is screwed into thread portion
589 of second annular cylindrical casing 420. Axial hole 590a is
formed through adjusting screw 590 so as to link small diameter
portion 244c of cavity 244 to the interior region of small diameter
section 422 of second annular cylindrical casing 420. Second coil
spring 584b is disposed between adjusting screw 590 and an upper
spherical surface of ball member 584a so as to urge ball member
584a downwardly by virtue of the restoring force of second coil
spring 584b. The restoring force of second coil spring 584b is
adjusted by the changes in the axial position of adjusting screw
590. Ball member 584a and second coil spring 584b substantially
form safety valve device 584.
Conduit 247 is formed in rear end plate 24 so as to link small
diameter portion 244c of cavity 244 to suction chamber 241. Conduit
248 is also formed in rear end plate 24 so as to link large
diameter portion 244a of cavity 244 to hole 256.
In this second embodiment of the present invention, the interior
region of the large diameter section 421 of second casing 420 is
linked to crank chamber 22 via holes 424, large diameter portion
244a of cavity 244, conduit 248, hole 256, conduit 212, central
bore 210, hole 221, hole 231 and gap 31a. Thus, the top end surface
of diaphragm 418 is in communication with and thereby receives the
refrigerant at the crank chamber pressure. Accordingly, the
capacity of compressor 10 is adjusted to maintain a predetermined
constant pressure in crank chamber 22, which in turn, also
maintains a predetermined constant pressure in suction chamber 241,
eventually.
This invention has been described in connection with preferred
embodiments. These embodiments, however, are merely for example
only and the invention is not restricted thereto. It will be
understood by those skilled in the art that variations and
modifications can easily be made within the scope of this invention
as defined by the claims.
* * * * *